It has been almost 20 years since the discovery by Kohler and Milstein of the technology to produce monoclonal antibodies (MAbs), a discovery that promised revolutionary changes in research, clinical diagnosis and human therapy. From today's perspective, it is fair to conclude that this promise has been realized in two areas of the three. As research tools, MAbs have been invaluable: their ability to selectively bind and localize specific antigens, detect and identify new ligands and their receptors, and agonize and/or antagonize specific molecular interactions continues to provide a useful...